Being in the family jewelry business, Kwiat brand manager Russell Kwiat knows a thing or two about diamond rings. In fact, all his expertise paid off this past December when he popped the question to his girlfriend. Despite obvious pressure to design the perfect engagement ring, he said he simply followed his own advice... and it paid off. (She said yes!) Here he shares his tips on getting the ring size, choosing a style she'll love and avoiding the biggest ring-shopping mistake.

What are some ways a guy can get his girlfriend's ring size—without asking?

When she's not looking, borrow a ring from her jewelry box. Select a ring you know she wears on her ring finger and then take it to a local jeweler to have them measure it. If you think she might notice that it's missing, place the ring as far down on your finger as it fits comfortably, then mark your finger with a pen. You can also trace the inside of the ring on a piece of paper or make an impression of it in a bar of soap. The trick is to get as close as possible to her size, you just don't want to guess. I also suggest asking her best friend—girls discuss these things. Just make sure you talk to a friend you trust to keep a secret. And finally, you can also take her shopping to look at rings, it's not uncommon. Have a sales associate take her finger size for future knowledge.

What is most important when purchasing a quality ring?

Work with a jeweler you trust and have confidence in the brand from which you are buying. Look for a brand that does everything from start to finish—from the manufacturing of the diamond to the production of the setting—and maintains the highest level of quality in both the diamond and the setting. People can see quality even if they don't understand diamonds or jewelry and will forever compliment her on her beautiful ring.

How should a guy go about picking out a ring that suits his girlfriend's style?

Pay Attention! She'll find ways to tell you what type of rings and diamond shapes she does and doesn't like. Whether it's a friend's or coworker's ring, or an ad in a magazine, she will make comments intended for you to hear. You need to listen to her and gather as much information as you can. This ring is about her and her personal style. But if she hasn't dropped any hints, I would turn to one of her friends or a sister for help and go shopping with her.

Are more and more women having a say in the engagement ring selection?

Absolutely! One of the biggest trends is that women are getting more involved. There is more talk than ever that goes into the ring selection. It's more socially accepted for a woman to talk about what she wants in a ring and more and more couples are shopping together to make sure the perfect ring is selected. Every women wants her own personal style reflected in the ring.

What's the biggest mistake men make when picking out an engagement ring?

Trying to shop for the best deal. Beauty and quality cost money. Too many guys try to do whatever it takes to not spend money or to get a good deal and it is reflected in the engagement ring. This is the most special woman in your life and this ring and everything that went into finding and creating it should reflect this. If money is a concern, know that there's a perfect diamond for every budget—it may just mean going a little smaller on the size you want. There are also settings that make the diamond look larger. Look for mountings with side stones—like pear-shaped accents that enhance a round center stone—or pavé diamonds that frame the center diamond.

Bonus question: How did you propose to your fiancée?

I did it on my birthday because I was afraid she might know the proposal was coming and she would never suspect that I'd ask on that day. I took her back to the place where we first ran into each other—the streets of Manhattan.